diff --git a/vlib/os/const_nix.c.v b/vlib/os/const_nix.c.v
index 70311303ae..dcacdd22da 100644
--- a/vlib/os/const_nix.c.v
+++ b/vlib/os/const_nix.c.v
@@ -6,6 +6,7 @@ const (
 	o_wronly	= 000000001 // open the file write-only.
 	o_rdwr		= 000000002 // open the file read-write.
 	o_create	= 000000100 // create a new file if none exists.
+	o_binary    = 000008000 // input and output is not translated.
 	o_excl		= 000000200 // used with o_create, file must not exist.
 	o_noctty	= 000000400 // if file is terminal, don't make it the controller terminal
 	o_trunc		= 000001000 // truncate regular writable file when opened.
diff --git a/vlib/os/const_windows.c.v b/vlib/os/const_windows.c.v
index d7b2436ee8..985458ac07 100644
--- a/vlib/os/const_windows.c.v
+++ b/vlib/os/const_windows.c.v
@@ -100,6 +100,7 @@ const (
 	o_rdwr                             = 0x0002 // open the file read-write.
 	o_append                           = 0x0008 // append data to the file when writing.
 	o_create                           = 0x0100 // create a new file if none exists.
+	o_binary                           = 0x8000 // input and output is not translated.
 	o_trunc                            = 0x0200 // truncate regular writable file when opened.
 	o_excl                             = 0x0400 // used with o_create, file must not exist.
 	o_sync                             = 0x0000 // open for synchronous I/O (ignored on Windows)
diff --git a/vlib/os/os.v b/vlib/os/os.v
index f3115e005e..93db502168 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -267,6 +267,7 @@ pub fn open_file(path string, mode string, options ...int) ?File {
 		match m {
 			`r` { flags |= o_rdonly }
 			`w` { flags |= o_create | o_trunc }
+			`b` { flags |= o_binary }
 			`a` { flags |= o_create | o_append }
 			`s` { flags |= o_sync }
 			`n` { flags |= o_nonblock }
diff --git a/vlib/os/os_test.v b/vlib/os/os_test.v
index b84c924004..b97a4171ca 100644
--- a/vlib/os/os_test.v
+++ b/vlib/os/os_test.v
@@ -4,23 +4,23 @@ const (
 	// tfolder will contain all the temporary files/subfolders made by
 	// the different tests. It would be removed in testsuite_end(), so
 	// individual os tests do not need to clean up after themselves.
-	tfolder = os.join_path( os.temp_dir(), 'v', 'tests', 'os_test')
+	tfolder = os.join_path(os.temp_dir(), 'v', 'tests', 'os_test')
 )
 
 fn testsuite_begin() {
 	eprintln('testsuite_begin, tfolder = $tfolder')
-	os.rmdir_all( tfolder )
-	assert !os.is_dir( tfolder )
-	os.mkdir_all( tfolder )
-	os.chdir( tfolder )
-	assert os.is_dir( tfolder )
+	os.rmdir_all(tfolder)
+	assert !os.is_dir(tfolder)
+	os.mkdir_all(tfolder)
+	os.chdir(tfolder)
+	assert os.is_dir(tfolder)
 }
 
 fn testsuite_end() {
-	os.chdir( os.wd_at_startup )
-	os.rmdir_all( tfolder )
-	assert !os.is_dir( tfolder )
-	//eprintln('testsuite_end  , tfolder = $tfolder removed.')
+	os.chdir(os.wd_at_startup)
+	os.rmdir_all(tfolder)
+	assert !os.is_dir(tfolder)
+	// eprintln('testsuite_end  , tfolder = $tfolder removed.')
 }
 
 fn test_open_file() {
@@ -43,6 +43,27 @@ fn test_open_file() {
 	os.rm(filename)
 }
 
+fn test_open_file_binary() {
+	filename := './test1.dat'
+	hello := 'hello \n world!'
+	os.open_file(filename, 'r+', 0o666) or {
+		assert err == 'No such file or directory'
+		os.File{}
+	}
+	mut file := os.open_file(filename, 'wb+', 0o666) or {
+		panic(err)
+	}
+	bytes := hello.bytes()
+	file.write_bytes(bytes.data, bytes.len)
+	file.close()
+	assert hello.len == os.file_size(filename)
+	read_hello := os.read_bytes(filename) or {
+		panic('error reading file $filename')
+	}
+	assert bytes == read_hello
+	os.rm(filename)
+}
+
 fn test_file_get_line() {
 	filename := './fgetline.txt'
 	os.write_file(filename, 'line 1\nline 2')
@@ -50,12 +71,16 @@ fn test_file_get_line() {
 		assert false
 		return
 	}
-	line1 := f.get_line() or { '' }
-	line2 := f.get_line() or { '' }
+	line1 := f.get_line() or {
+		''
+	}
+	line2 := f.get_line() or {
+		''
+	}
 	f.close()
 	//
-	//eprintln('line1: $line1')
-	//eprintln('line2: $line2')
+	// eprintln('line1: $line1')
+	// eprintln('line2: $line2')
 	assert line1 == 'line 1\n'
 	assert line2 == 'line 2'
 }
@@ -74,9 +99,9 @@ fn test_create_file() {
 
 fn test_is_file() {
 	// Setup
-	work_dir := os.join_path(os.getwd(),'is_file_test')
+	work_dir := os.join_path(os.getwd(), 'is_file_test')
 	os.mkdir_all(work_dir)
-	tfile := os.join_path(work_dir,'tmp_file')
+	tfile := os.join_path(work_dir, 'tmp_file')
 	// Test things that shouldn't be a file
 	assert os.is_file(work_dir) == false
 	assert os.is_file('non-existent_file.tmp') == false
@@ -88,7 +113,7 @@ fn test_is_file() {
 	$if windows {
 		assert true
 	} $else {
-		dsymlink := os.join_path(work_dir,'dir_symlink')
+		dsymlink := os.join_path(work_dir, 'dir_symlink')
 		os.system('ln -s $work_dir $dsymlink')
 		assert os.is_file(dsymlink) == false
 	}
@@ -96,7 +121,7 @@ fn test_is_file() {
 	$if windows {
 		assert true
 	} $else {
-		fsymlink := os.join_path(work_dir,'file_symlink')
+		fsymlink := os.join_path(work_dir, 'file_symlink')
 		os.system('ln -s $tfile $fsymlink')
 		assert os.is_file(fsymlink)
 	}
@@ -117,35 +142,27 @@ fn test_write_and_read_string_to_file() {
 // test_write_and_read_bytes checks for regressions made in the functions
 // read_bytes, read_bytes_at and write_bytes.
 fn test_write_and_read_bytes() {
-	file_name :=  './byte_reader_writer.tst'
-	payload   :=  [byte(`I`), `D`, `D`, `Q`, `D`]
-
+	file_name := './byte_reader_writer.tst'
+	payload := [byte(`I`), `D`, `D`, `Q`, `D`]
 	mut file_write := os.create(os.real_path(file_name)) or {
 		eprintln('failed to create file $file_name')
 		return
 	}
-
 	// We use the standard write_bytes function to write the payload and
 	// compare the length of the array with the file size (have to match).
 	file_write.write_bytes(payload.data, 5)
-
 	file_write.close()
-
 	assert payload.len == os.file_size(file_name)
-
 	mut file_read := os.open(os.real_path(file_name)) or {
 		eprintln('failed to open file $file_name')
 		return
 	}
-
 	// We only need to test read_bytes because this function calls
 	// read_bytes_at with second parameter zeroed (size, 0).
 	rbytes := file_read.read_bytes(5)
-
 	// eprintln('rbytes: $rbytes')
 	// eprintln('payload: $payload')
 	assert rbytes == payload
-
 	// check that trying to read data from EOF doesn't error and returns 0
 	mut a := []byte{len: 5}
 	nread := file_read.read_bytes_into(5, a) or {
@@ -153,7 +170,6 @@ fn test_write_and_read_bytes() {
 		int(-1)
 	}
 	assert nread == 0
-
 	file_read.close()
 	// We finally delete the test file.
 	os.rm(file_name)
@@ -212,42 +228,42 @@ fn test_cp() {
 }
 
 fn test_mv() {
-	work_dir := os.join_path(os.getwd(),'mv_test')
+	work_dir := os.join_path(os.getwd(), 'mv_test')
 	os.mkdir_all(work_dir)
 	// Setup test files
-	tfile1 := os.join_path(work_dir,'file')
-	tfile2 := os.join_path(work_dir,'file.test')
-	tfile3 := os.join_path(work_dir,'file.3')
+	tfile1 := os.join_path(work_dir, 'file')
+	tfile2 := os.join_path(work_dir, 'file.test')
+	tfile3 := os.join_path(work_dir, 'file.3')
 	tfile_content := 'temporary file'
 	os.write_file(tfile1, tfile_content)
 	os.write_file(tfile2, tfile_content)
 	// Setup test dirs
-	tdir1 := os.join_path(work_dir,'dir')
-	tdir2 := os.join_path(work_dir,'dir2')
-	tdir3 := os.join_path(work_dir,'dir3')
+	tdir1 := os.join_path(work_dir, 'dir')
+	tdir2 := os.join_path(work_dir, 'dir2')
+	tdir3 := os.join_path(work_dir, 'dir3')
 	mkdir(tdir1)
 	mkdir(tdir2)
 	// Move file with no extension to dir
-	os.mv(tfile1,tdir1)
-	mut expected := os.join_path(tdir1,'file')
+	os.mv(tfile1, tdir1)
+	mut expected := os.join_path(tdir1, 'file')
 	assert os.exists(expected) && !is_dir(expected) == true
 	// Move dir with contents to other dir
-	os.mv(tdir1,tdir2)
-	expected = os.join_path(tdir2,'dir')
+	os.mv(tdir1, tdir2)
+	expected = os.join_path(tdir2, 'dir')
 	assert os.exists(expected) && is_dir(expected) == true
-	expected = os.join_path(tdir2,'dir','file')
+	expected = os.join_path(tdir2, 'dir', 'file')
 	assert os.exists(expected) && !is_dir(expected) == true
 	// Move dir with contents to other dir (by renaming)
-	os.mv(os.join_path(tdir2,'dir'),tdir3)
+	os.mv(os.join_path(tdir2, 'dir'), tdir3)
 	expected = tdir3
 	assert os.exists(expected) && is_dir(expected) == true
 	assert os.is_dir_empty(tdir2) == true
 	// Move file with extension to dir
-	os.mv(tfile2,tdir2)
-	expected = os.join_path(tdir2,'file.test')
+	os.mv(tfile2, tdir2)
+	expected = os.join_path(tdir2, 'file.test')
 	assert os.exists(expected) && !is_dir(expected) == true
 	// Move file to dir (by renaming)
-	os.mv(os.join_path(tdir2,'file.test'),tfile3)
+	os.mv(os.join_path(tdir2, 'file.test'), tfile3)
 	expected = tfile3
 	assert os.exists(expected) && !is_dir(expected) == true
 }
@@ -415,9 +431,9 @@ fn test_is_abs() {
 
 fn test_join() {
 	$if windows {
-		assert os.join_path('v','vlib','os') == 'v\\vlib\\os'
+		assert os.join_path('v', 'vlib', 'os') == 'v\\vlib\\os'
 	} $else {
-		assert os.join_path('v','vlib','os') == 'v/vlib/os'
+		assert os.join_path('v', 'vlib', 'os') == 'v/vlib/os'
 	}
 }
 
@@ -469,8 +485,8 @@ fn test_write_file_array_bytes() {
 		panic(err)
 	}
 	assert arr == rarr
-	//eprintln(arr.str())
-	//eprintln(rarr.str())
+	// eprintln(arr.str())
+	// eprintln(rarr.str())
 }
 
 fn test_write_file_array_structs() {
@@ -483,5 +499,5 @@ fn test_write_file_array_structs() {
 	rarr := os.read_file_array<IntPoint>(fpath)
 	assert rarr == arr
 	assert rarr.len == maxn
-	//eprintln( rarr.str().replace('\n', ' ').replace('},', '},\n'))
+	// eprintln( rarr.str().replace('\n', ' ').replace('},', '},\n'))
 }